1. Field of the Invention
The present invention relates to methods and devices for controlling or regulating physical variables of systems. More particularly, this invention pertains to methods and devices for controlling or regulating dynamic systems employing phase modulators.
2. Description of the Prior Art
Micromechanical sensors comprise known art. Coriolis gyroscopes (a.k.a. “vibration gyroscopes”), normally employed to measure rotational speeds, are prominent examples of such sensors. Such gyroscopes include a mass system that is caused to vibrate. The vibration is normally the superposition of a multiplicity of individual vibrations that are initially independent of each other and can be regarded in the abstract in each case as “resonators”. At least two resonators are required for gyroscope operation. A first resonator is artificially excited to vibrate (“excitation vibration”). The second resonator is then excited to vibrate when the Coriolis gyroscope is moved or rotated. In such a situation, Coriolis forces occur that couple the first resonator to the second resonator, extracting energy from the excitation vibration of the first resonator and transferring that energy to the readout vibration of the second resonator (“readout vibration”). In order to determine movements (e.g. rotations) of the Coriolis gyroscope, the readout vibration is picked up and a corresponding readout signal (“readout vibration pick-off signal”) is examined to ascertain whether changes in amplitude of the readout vibration, which represent a measure of rotation of the Coriolis gyroscope, have occurred. Coriolis gyroscopes can be implemented as both open-loop and closed-loop systems in which the amplitude of readout vibration is continuously reset to a fixed value (preferably zero) by means of a control loop.
In the discussion that follows, “resonator” should be understood to refer to a vibratory mass system (possibly including mechanical springs) while “vibrator” is employed as a synonym for this.
Reference is made, for example, to German patent application DE 102 48 733 A1 for a detailed discussion of Coriolis gyroscope functionality. A disadvantage of existing Coriolis gyroscopes such as that described in DE 102 48 733 A1 is that a plurality of digital-analog converters is required to generate corresponding force impulses from the digital reset or regulating signals. Digital-analog converters are expensive, require considerable electrical power and are relatively unsuitable for integration with other electronic components, thereby limiting miniaturization.